Scientists stunned after witnessing unprecedented cascade triggered by common fishing practice: ‘Collective memory loss’

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Scientists stunned after witnessing unprecedented cascade triggered by common fishing practice: ‘Collective memory loss’

The world’s largest herring population has experienced an unprecedented 800-kilometer (497-mile) shift in its spawning grounds because of fishing practices that target older fish, according to a study in the journal

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What’s happening?

Norwegian spring spawning herring have traditionally migrated up to 1,300 kilometers (808 miles) southward from northern Norwegian waters to spawn at the west coast, a journey that helps ensure better survival rates for their offspring.

However, new research shows these fish have abruptly shifted their spawning grounds northward after heavy fishing pressure targeted older, more experienced fish that typically “teach” migration routes to younger generations.

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that when fisheries selectively harvested older herring, it created a “collective memory loss” within the population, disrupting long-established migration patterns.

The change occurred when a large cohort of young herring emerged in 2016, when the population of older fish had plummeted by 68%. Without enough elder “guides,” these young fish established their own, shorter migration routes that older survivors eventually adopted.

Why is this migration shift concerning?

This disruption in fish migration doesn’t just affect herring. It impacts entire coastal ecosystems and communities that depend on these spawning events.

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When herring spawn in southern areas, their eggs and hatched larvae spread over larger areas during their northward drift, enriching diverse coastal ecosystems. Local predatory fish, endangered seabird colonies, and even coastal communities benefit from this natural energy distribution pattern along the Norwegian coast.

The shift could lead to lower fish production over time, as the northward spawning areas may not provide the same survival advantages for young fish. For you at home, this could eventually mean fewer herring available in grocery stores and higher prices for this nutritious seafood option.

The research also raises broader concerns about how current fishing practices might be disrupting important animal behaviors that have evolved over centuries. If fish can’t pass down their migration knowledge, we may see similar problems affect other commercial fish species, potentially threatening food security for communities worldwide.

What’s being done about harmful fishing practices?

Scientists are advocating for “longevity conservation” in fisheries management — namely, policies that protect older fish instead of focusing on overall population numbers. Maintaining a healthy age structure in fish preserves their collective knowledge and cultural behaviors.

Some fisheries are already exploring finer-scale management strategies that protect fish at different life stages and locations, rather than treating entire populations as single units.

If you want to help,

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certified by organizations like the Marine Stewardship Council, which promotes sustainable fishing practices. You can also use seafood guides from groups like Seafood Watch to choose fish harvested using methods that minimize ecosystem impacts.

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